In Vitro Ovicidal and Larvicidal Activities of Stem Bark of Terminalia glaucescens (Combretaceae) against Haemonchus contortus

Objectives: To evaluate the in vitro activity of aqueous and methanolic extracts of stem bark of Terminalia glaucescens on the eggs and larval stages of Haemonchus contortus of sheep. Methods: The eggs were exposed for 24 hours in five different concentrations (625, 1250, 2500, 3750 and 5000 μg/ml) of methanol, hot water (decoction) and cold water extracts at room temperature (25 ̊C). Distilled water, 1.25% DMSO and Albendazole were used as negatives and positive control respectively in the bioassay. Results: A significant effect was obtained with all of the three extracts and differences were observed depending on the parasitic stage. Hot water extract (HWE), Methanol (MET) and Cold water extract (CWE) inhibited embryonic development by 98.1%, 96% and 86.5% respectively at 5000 μg/ml, meanwhile Albendazole had a 77.9% inhibition. For the mean inhibition rate of egg hatching, there was a general increase in the inhibition rate with increase in concentration of the extract from 625 to 5000 μg/ml. Methanol extract had the highest inhibition rate in all concentration from 625 to 5000 μg/ml. Concerning larval mortality, HWE had the highest effect in L1 larval mortality in all concentration above 1250 μg/ml. Distilled water had very little larval mortality on L1 and L2 larvae by 3.3 and 3.3% respectively. Conclusion: This in vitro study brought out the ovicidal and larvicidal properties of stem bark of Terminalia glaucescens.